Foam forming unit

ABSTRACT

A foam-forming unit is disclosed. The foam-forming unit includes a mixing chamber communicating with the outlet of a pump for the purpose of mixing liquid and air, and includes a dispensing part provided with an outflow channel with a foam opening for dispensing foam, wherein the outflow channel is in communication with the mixing chamber. Further, a first foam-forming element is included, arranged in the outflow channel such that the foam flowing through the outflow channel passes through the foam-forming element at least twice. The dispensing part is further provided with a spout element in which is located the final part of the outflow channel and the foam opening. Finally, the outflow channel includes a cavity after the first passage through the first foam-forming element, which cavity lies before the spout element as seen in flow direction.

The invention relates to a foam-forming unit which comprises a mixingchamber for mixing liquid and air, a dispensing part provided with anoutflow channel with a foam opening for dispensing foam, wherein theoutflow channel is in communication with the mixing chamber, and a firstfoam-forming element arranged in the outflow channel such that the foamflowing through the outflow channel passes through the foam-formingelement at least twice, wherein the dispensing part is further providedwith a spout element in which is located the final part of the outflowchannel and the foam opening.

Such a foam-forming unit is known from EP 1 199 105. Arranged in thespout element is the foam-forming element through which the foam passestwice on its way to the foam opening in the spout element. Thedimensions of the foam-forming element are limited by the limitedinternal dimensions of the spout element.

The invention has for its object to provide an improved foam-formingunit. A further object of the invention is to provide a foam-formingunit with which a foam of the highest possible quality can be produced,i.e. air bubbles in the foam being as fine and as uniform as possible.

The present invention provides for this purpose a foam-forming unit ofthe type described in the introduction, wherein the outflow channelcomprises a cavity after the first passage through the firstfoam-forming element, which cavity lies before the spout element as seenin flow direction.

The space in the cavity, which the foam enters when it has passedthrough the first foam-forming element for a first time, can be readilyadjusted in respect of dimensions. The cavity lies under the cap of thedispensing part which, from a production engineering viewpoint, can beeasily adapted to the desired situation. The cavity, and thereby thecounter-pressure, is important in creating a resistance whereby the foamis as it were forced to pass through the foam-forming element at adetermined speed. The ability to vary the counter-pressure is importantin respect of the application of diverse liquids for pumping. Thequality of the foam can therefore be further influenced in a simplemanner by the correct choice of the dimensions of the cavity.

Because the foam flowing through the outflow channel passes through thefoam-forming element twice, a finer and more uniform foam is found toresult. In addition, the production process is relatively simple, sinceonly one foam-forming element is arranged for two passages, which hasthe effect of saving costs.

In a preferred embodiment a screen foam-forming element is arranged inthe outflow channel before the first foam-forming element. This is foundto further improve the quality of the dispensed foam.

In a preferred embodiment the foam-forming element comprises a screen. Ascreen is found to produce the desired foam-forming effect.

In a further embodiment the foam-forming element comprises a mixingelement in addition to or instead of a screen. A screen has the objectof reducing the particle size, while a mixing element brings about amixing or swirling of the foam.

In a preferred embodiment the openings in the second screen have adimension between 0.1 mm and 0.4 mm, and preferably in the order of 0.2mm. Tests have shown that these dimensions produce the desired results.

In a preferred embodiment the first screen has openings with a dimensionbetween 10 μm and 150 μm, and preferably in the order of 50 μm. Testshave shown that these dimensions produce the desired results.

The foam-forming unit further comprises a pump for liquid and a pump forair, which are each provided with an inlet and an outlet.

In a preferred embodiment the foam-forming unit comprises valves in theinlet and the outlet of each pump for drawing in respectively expellingair and liquid, wherein one or more valves are formed integrally withthe air pump or liquid pump into a single construction element. Integralforming of the valves reduces the number of components and productionsteps and saves costs.

In a preferred embodiment the outflow channel comprises, after the firstpassage through the first screen, a cavity comprising side walls and anupper wall with a predetermined height relative to the first screen. Asexplained above, the dimension of the cavity is found in practice to beimportant in producing foam of a higher quality.

In a further preferred embodiment the predetermined height is between 1mm and 4 mm, and preferably in the order of 2 mm. With such dimensionsthe foam-forming unit is found in practice to produce finer and moreuniform foam.

In a further preferred embodiment a cap forms the walls of the cavity.The cap is simple to arrange and enables a greater variety in theproduct, including variation in colour and material choice.

In a further preferred embodiment the inlet of the pump for aircomprises at least one opening for drawing in air in an outer wall ofthe foam-forming unit. Owing to this location of the air opening thefoam-forming unit can also be used in a wet environment, such as ashower, without water interfering with the operation.

In a further preferred embodiment the above mentioned openingcommunicates with a space in which a tube, which communicates with anair reservoir of the air pump, protrudes over a predetermined length.Owing to such an air inlet the foam-forming unit will continue tofunction in a wet environment such as a shower. The opening can also berelatively small and therefore inconspicuous.

According to a further aspect, the present invention provides a foamdispensing assembly consisting of a liquid container and a foam-formingunit, wherein the foam-forming unit is formed by a foam-forming unit asdescribed above.

The invention will now be further elucidated with reference to theannexed drawings. In the drawings:

FIG. 1 shows a perspective, partly cut-away foam dispensing assemblyaccording to the invention;

FIG. 2 shows a perspective view in cross-section of a detail of afoam-forming unit according to the present invention;

FIG. 3 is a partly cut-away detail view of the foam-forming unit of FIG.2, and

FIG. 4 is a perspective view in cross-section of a detail of afoam-forming unit according to a second embodiment.

A foam dispensing assembly 1 according to the present inventioncomprises a cylindrical liquid container 2 which has therein a liquid 3for foaming and on which is arranged a foam-forming unit 4 (FIG. 1).Foam-forming unit 4 comprises a pump 6 for air and a pump 8 for liquid,which are each provided with an inlet and outlet. Inlet 9 of air pump 6is in communication with the environment (FIG. 2), while the inlet ofliquid pump 8 is in communication with the content 3 of liquid container2 via hose 10. Foam-forming unit 4 further comprises a mixing chamber 12which is in communication with outlet 14 of air pump 6 and the outlet ofliquid pump 8 comprising valve 16. Valve 18 is further arranged close tothe outlet of the air pump.

The top part of the assembly comprises a dispensing part 22, comprisingan outflow channel 24 with a foam opening 26 (FIG. 2). Outflow channel24 runs from mixing chamber 12 to foam opening 26. In this channel 24are arranged foam-forming elements, in the embodiment shown in FIG. 2 inthe form of relatively fine-mesh screens 34,28.

A first screen 28 is arranged by means of ultrasonic welding such thatthe foam passes through screen 28 twice. Arranged for this purpose abovescreen 28 is a cap 30 which forms a cavity 32 above screen 28. As seenin the flow direction, cavity 32 is located before spout element 51. Theupper wall of cap 30 is curved for the purpose of simple and ergonomicoperation. The minimum height, i.e. the distance between cap 30 andscreen 28, is about 2 mm, which tests have shown to be an advantageousheight for finer and more uniform foam. Screen 28 has openings with adimension between 10 μm and 150 μm, and preferably in the order of 50μm. Cap 30 is a separate component of the foam-forming unit, which makespossible a variation in colour and material thereof.

In the shown preferred embodiment a second screen 34 is further arrangedin the outflow channel before the first screen, which has openings witha dimension between 0.1 mm and 0.4 mm, and preferably in the order of0.2 mm. The second screen 34 is arranged by injection moulding and isformed integrally with a ring 35 which forms part of constructioncomponent 61. Two components of the foam-forming unit are thusintegrated, thereby reducing the cost price and assembly time.

The mixture of liquid and air leaves the mixing chamber 12 via secondscreen 34, wherein foam is formed with a relatively coarse structure.The coarse foam then passes through the first screen 28 and enterscavity 32, wherein the structure of the foam becomes finer and moreuniform, i.e. air bubbles in the foam are of smaller and more uniformsize. The foam then passes through screen 28 a second time andapproaches outflow opening 26, wherein the foam becomes even finer andmore uniform.

The quality of the foam is higher than in known foam-forming units,which often also comprise two screens. In addition, only one productionstep is necessary to arrange the first screen, so that production costsare still about the same as for known foam-forming units. For a furtherimprovement in the foam quality, a third screen (not shown) can bearranged on edge 36.

In a further preferred embodiment the air inlet of the air pump isformed by a gap 37 arranged between cap 30 and wall 38 (FIG. 3). Air isdrawn in and enters space 40 into which debouches a tube 42, whichserves as a chimney and allows the air through to air chamber 44 for theair pump. The upper end 46 of tube 42 is preferably angled, wherein theangle with the longitudinal axis of the tube is about 30°. Tube 42protrudes over a predetermined length of about 4 mm into space 40. Theconstruction thus acts as an enclosed chimney. This air inlet has theadvantage that in a wet environment hardly any water is drawn in, sothat the foam-forming unit also continues to function under the shower.

FIG. 4 shows a second embodiment of a foam-forming unit according to theinvention. The embodiment is largely identical to the first embodimentshown in FIG. 2, with the difference that a further foam-forming elementin the form of a mixing element 50 is placed in outflow channel 24.Mixing element 50 is arranged between first foam-forming element 28 andsecond foam-forming element 34 a. Mixing element 50 consists of aplate-like element which is co-moulded with construction component 60and which is provided with four circular holes with a cross-section ofabout 1.5 mm. The pattern and dimensions of the openings in mixingelement 50 can be varied subject to the product for pumping. Anadditional second foam-forming element 34 b can be further provided(location of this element is shown in FIG. 4).

It is noted that the second foam-forming element 34 a is preferablyco-moulded with construction component 61. The additional secondfoam-forming element 34 b is preferably welded to the upper side ofconstruction component 61. The first foam-forming element 28 ispreferably also welded to the upper edge 36 of construction component60. The foam-forming unit consists substantially of only threeconstruction components 60, 61 and 32.

The further operation of the above described foam-forming unit 4 andassembly 1 is described in the international patent application 0 242005 of applicant. The content thereof is incorporated herein.

The system has a variable arrangement, wherein a number of options areavailable for adapting the foam-forming unit to a specific liquid.Because there are very diverse liquids (viscosity, tixotropic behaviour,chemical composition, the presence of particles etc.), there is a systemarrangement wherein the construction can be modified relatively easilyto the liquid for pumping. The variables are, among others, number,pattern and size of the openings in the or each foam-forming element,the number of foam-forming elements, which foam-forming elements (screenor mixing element), dimensions of cavity 32 and so on.

The present invention is not limited to the above described preferredembodiments thereof, in which many modifications can be envisaged, butis defined by the scope of the appended claims.

1. Foam-forming unit, comprising: a mixing chamber communicating with the outlet of a pump for the purpose of mixing liquid and air, a dispensing part provided with an outflow channel with a foam opening for dispensing foam, the outflow channel being in communication with the mixing chamber, and a first foam-forming element arranged in the outflow channel such that the foam flowing through the outflow channel passes through the foam-forming element at least twice, the dispensing part further including a spout element in which is located the final part of the outflow channel and the foam opening, and the outflow channel including a cavity after the first passage through the first foam-forming element, the cavity lying before the spout element as seen in flow direction.
 2. Foam-forming unit as claimed in claim 1, wherein a second foam-forming element is arranged in the outflow channel.
 3. Foam-forming unit as claimed in claim 1, wherein the foam-forming element comprises a screen.
 4. Foam-forming unit as claimed in claim 1, wherein the foam-forming element comprises a mixing element.
 5. Foam-forming unit as claimed in claim 1, further comprising a pump for liquid and a pump for air, which are each provided with an inlet and an outlet.
 6. Foam-forming unit as claimed in claim 5, comprising valves in the inlet and the outlet of each pump for drawing in respectively expelling air and liquid, wherein one or more valves are formed integrally with the air pump or liquid pump into a single construction element.
 7. Foam-forming unit as claimed in claim 3, wherein the screen of the first foam-forming element has openings with a dimension between 10 μm and 150 μm.
 8. Foam-forming unit as claimed in claim 3, wherein the openings in the screen of the second foam-forming element have a dimension between 0.1 mm and 0.4 mm.
 9. Foam-forming unit as claimed in claim 1, wherein the outflow channel comprises after the first passage through the first foam-forming element a cavity comprising side walls and an upper wall with a predetermined height relative to the first foam-forming element.
 10. Foam-forming unit as claimed in claim 9, wherein the predetermined height is between 1 mm and 4 mm.
 11. Foam-forming unit as claimed in claim 9, wherein a cap forms the walls of the cavity and wherein the upper wall is curved.
 12. Foam-forming unit as claimed in claim 11, wherein the cap is arranged on inner walls of the foam-forming unit in order to form the cavity.
 13. Foam-forming unit as claimed in claim 5, wherein the inlet of the pump for air comprises at least one opening for drawing in air in an outer wall of the foam-forming unit.
 14. Foam-forming unit as claimed in claim 13, wherein the opening for drawing in air is in communication with a space in which a tube, which communicates with an air reservoir of the air pump, protrudes over a predetermined length.
 15. Foam dispensing assembly comprising a liquid container and a foam-forming unit, wherein the foam-forming unit is formed by a foam-forming unit as claimed in claim
 1. 16. Method, comprising: manufacturing a foam-forming unit as claimed in claim
 1. 17. Method, comprising: using a foam-forming unit as claimed in claim
 1. 18. Method, comprising: manufacturing a foam dispensing assembly as claimed in claim
 15. 19. Method, comprising: using a foam dispensing assembly claimed in claim
 15. 